Darius na
simplemind ishu iko hivi:
Ay" + By' + Cy = D + E(sinwt).
This is a form of equation where A, B, C, D, E and w are constants and t is a parameter.
Now separate the equation:
Ay" + By' + Cy = D........
Equation i
Ay" + By' + Cy = E(sinwt).........
Equation ii
Then;
For Equation i
Ay" + By' + Cy = D is in form of f(X) = M ,where M is a constant and f(X) = y. Thus y = M
So if y = M; Then y' = 0 and y" = 0. Since we differentiating constant number, all derivatives become zero ( 0 ).
Then substitute the values above in
Equation i
From: Ay'' + By' + Cy = D where y = M; y' = 0 and y" = 0
Then: A(0) + B(0) + C(M) = D
Then: C(M) = D , thus the value of M = D/C but M = f(x) = y
Thus the value of y = D/C
For Equation ii
Ay'' + By' + Cy = E(sinwt) is in form of f(X) = M(sinwt) + N(coswt) and f(X) = y.
Thus y = M(sinwt) + N(coswt)
So if, y = M(sinwt) + N(coswt)
Then y' =Mw(coswt) - Nw(sinwt)
Then y'' = -Mw(sinwt) - Nw(coswt)
Substitute the values above into
Equation ii
A(-Mw(sinwt) - Nw(coswt)) + B(Mw(coswt) - Nw(sinwt)) + C(M(sinwt) + N(coswt)) = E(sinwt)
-AMw(sinwt) - ANw(coswt) + BMw(coswt) - BNw(sinwt) + CM(sinwt) + CN(coswt) = E(sinwt) + 0(coswt)
By comparing the values of Sine and Cosine:
For Sine
-AMw(sinwt) - BNw(sinwt) + CM(sinwt) = E(sinwt)......
Equation iii
We flash out (sinwt) and the equation will be: -AMw - BNw + CM = E
Then: M(C - Aw) - NBw = E ;
But (C - Aw) and Bw are both constants.
Then let (C - Aw) be m and Bw be m. Since all values are both constant.
Thus Mm - Nm = E.......
Equation iv
For Cosine
- ANw(coswt) + BMw(coswt) + CN(coswt) = 0(coswt)......
Equation v
We flash out (coswt) and the equation will be:
-ANw + BMw + CN = 0
N(C - Aw) + BMw = 0
But (C - Aw) & Bw are both constants.
Then Let (C - Aw) be n and Bw be n.
Thus: Nn + Mn = 0 .....
Equation vi
Thus by combining
Equation iv &
Equation vi we get;
Mm - Nm = E.......
Equation iv
Nn + Mn = 0 ........
Equation vi
Now, let us solve simultaneous equation to obtain the values of M & N where m and n are both constants.
In
Equation vi : Nn = -Mn
Thus N = -M, Since n and n are constants. And any valuable multiplied by constant, the answer will be constant.
So let constant M(n) be k .
Therefore the value of N will be - k.
Substitute the value of N = -k into
Equation iv
Mm - Nm = E;
We get Mm + km = E
Then Mm = E - km
Then M = (E - km)/m
So let constant (E - km)/m be k .
Therefore the value of M will be k.
Thus the value of y = k(sinwt) - k(coswt)
Since the value of y = y1 + y2. The overall value of y will be given as
y = D/C + k2(sinwt) - k1(coswt) where C, D, k1 and k2 are both cosntants